Fabricated tuyere nozzle

ABSTRACT

A tuyere nozzle for a metallurgical furnace fabricated from a plurality of functional elements joined together to form a completed tuyere nozzle. The tuyere nozzle includes a nose element through which the air enters the furnace, which is formed from high conductivity, oxygen free, rolled or forged copper to resist the most severe temperature and abrasion conditions encountered in a furnace, and the pipe element, which conveys the heated air through the tuyere, is formed from lower thermal conductivity metal, as stainless steel, or ceramic lined metal, to minimize air blast heat loss, controlled water flow for uniform cooling of the hot surfaces, and preferably corrosion resistant to resist the corrosive action of molten lime and slag.

United States P316111 1 Apr. 17, 1973 FOREIGN PATENTS OR APPLICATIONS 10/1920 Great Britain .;...266/41 3/1936 Germany ..266/41 A tuyere nozzle for a metallurgical furnace fabricated from a plurality of functional elements joined together to form a completed tuyere nozzle. The tuyere nozzle includes a nose element through which the air enters the fumace, which is formed from high conductivity, oxygen free, rolled or forged copper to resist the most severe temperature and abrasion conditions encountered in a furnace, and the pipe element, which conveys the heated air through the tuyere,.is formed from lower thermal conductivity metal, as stainless steel, or ceramic lined metal, to minimize air blast heat loss, controlled water flow for uniform cooling of the hot surfaces, and preferably corrosion resistant to resist the corrosive action of molten lime and slag.

Allen [541 FABRICATED TUYERE NOZZLE [76] Inventor: John E. Allen, 606 Timber Lane,

Lake Forest, 111.

[22] Filed: Feb. 22, 1971 [21] Appl.No.: 117,350

[52] U.S.C1 ..266/41 [51] Int. Cl. C2lb 7/16 [58] Field of Search ..1 10/1825; 122/66; 266/41 [56] References Cited I UNITED STATES PATENTS 399,263 3/1889 Hartman ..266/41 1,354,032 9/1920 'Dovel ....266/4l 1,673,053 6/1928 Ohba ...,266/41 2,023,025 12/1935 McKee ....266/41 2,145,650 1/1939 Fox ...122/6.6 2,200,497 5/1940 Fox ...122/6.6 2,827,279 3/1958 Cox ....266/41 2,828,956 4/1958 Bieniosek et a1. ....266/4l 3,234,919 2/1966 Troy.,...... ..122/6.6 3,341,188 9/1967 Armour et a1. ..110/182.5

9 Claims, 5 wing Figures PATHJTEU 1 W75 3. 727, 898

sum 1 BF 2 INVENTOR JOHN E ALLEN BY MMF%4J ATTORNEYS PATENTED 1 71975 SHEET 2 [IF 2 FIG.?)

FABRICATED TUYERE NOZZLE BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a tuyers nozzle for use in introducing hot air into a metallurgical furnace and, more particularly, to improvements in a tuyere nozzle for extending the tuyere nozzle life and maximize the efficiency thereof.

2. Description of the Problem and Development Work Underlying the Invention Blast furnaces are well known in the art of producing pig iron from iron ore. The bulk of the iron ore used is ferric oxide and the blast furnace provides a means to extract the oxygen from the oxide to produce the metallic iron. The reducing agent used is carbon in the form of coke. The reducing process is carried out at high temperatures which are obtained by the combustion of coke by high temperature air. The ore, iron oxide, is never found in a pure state nature and always contains a proportion of gangue composed of silica, alumina, lime, magnesia, etc., which has to be removed. At sufficiently high temperatures lime and silica combine along with the other earthy materials to form a liquid slag which is lighter than the liquid iron and, thus, separates from the molten metal and floats to the top.

The pig'iron produced is not pure iron but is about 91 percent pure iron combined with varying amounts of carbon, silicon, manganese, sulfur and phosphorous. Each constituent has an important affect on the quality of the pig iron, and thus to obtain a product of the quality required, the mass of material, the burden, from which the pig iron is made, contains, in addition to iron, the requisite proportions of the other constituents mentioned. Thus there is charged into the furnace: (l) the burden, which includes the iron ore, fluxes for forming the slag and other additions, e. g., manganese ore scrap or phosphoric rock; (2) the fuel, which is usually coke; and (3) the air blast which is injected through a tuyere into the hearth of the furnace to burn the fuel and to maintain the sufficiently high temperature to render both metal and slag freely molten.

The solid materials are charged into the top of the furnace while the air blast which is heated to approximately l,200 to 2,000F. to improve fuel economy, is blown under high pressure through tuyeres into the hearth where the highest temperatures (about 3,400F.) are generated. The oxygen of the air coming through the tuyere nozzle combines with the carbon of the coke, momentarily forming carbon dioxide which is subsequently converted into carbon monoxide, a powerful reducing agent. Hot carbon monoxide passes upward through the column of solid materials and chemically reacts therewith.

. The constituents of the burden pass through the furnace, usually in 6 to 12 hours, while the gas passes upward through the burden, usually in 3 to seconds. As the constituents slowly descend through the stack, the

temperature increases and the carbon monoxide gas,

combines with the oxygen of the iron oxide to fornicarbon dioxide and the metallic iron in a finely divided form called iron sponge. The separation does-not occur until near the top of the bosh (see FIG. 1) where both the iron and slag-begin to melt. The coke passes through the furnace with little change except the constant increase in temperature, until it reaches the tuyere zone, where intense combustion takes place with the oxygen of the air blast. The bosh and hearth are filled with coke and as the slag and iron melt, the liquids trickle down until they reach the well formed in the bottom of the hearth where they slowly accumulate and separate with the slag layer accumulating on top. The iron and slag are tapped from the furnace and the slag is skimmed off the top leaving the final pig iron product.

As can be appreciated from the foregoing description of a blast furnace operation, the tuyere nozzle must function under operating conditions of great severity. This is evidenced by the fact that the approximate average tuyere life is only 60 days. The work of replacing tuyeres every 60 days or less on an as required basis has been an economic burden on the iron producing industry for years. In addition, failure of a tuyere during operation of a blast furnace requires shutting down the furnace or may result in an off cast" or even in tuyere explosions. The advent of high production furnaces. in recent years has made the tuyere failure problem even more costly.

I believe that there are a number of factors which contribute to tuyere failure. Among these are the following:

1. Normal abrasion The tremendous activity which occurs at the outlet end of the tuyere, the nose, particularly the ceaseless swirling of particles of incandescent coke and the descension of charged materials into the combustion zone, eventually wears the nose so thin that small leaks develop;

2. Excessively high temperature Excessively high temperatures will cause the metal to crack and eventually melt. This high temperature usually results from the loss of cooling water effectiveness due to settleable solids blocking circulation entirely or leaving deposits which result in local overheating, entrained gases forming pockets that block water circulation, and poor water distribution in general;

3. Corrosion A sudden slip of the burden to the hearth may splash highly corrosive molten metal and slag into the interior of the tuyere nozzle and, thus, cause failure;

4. Iron cutting The oxidation of carbonous charged materials and sponge iron often cause failure. A formation of slag and/or coke on, or in, the vicinity of the bottom portion of the tuyere nozzle creates a pocket in which molten sponge iron collects. The continued presence of the molten metal at the nose of the tuyere nozzle eventually melts the nozzle at that point. For more background information refer to my paper published in TMS-AIME Ironmaking Proceedings, Vol. 29, Detroit 1970, beginning at page 154.

BRIEF DESCRIPTION OF THE PRIOR ART Various means have been suggested to overcome the aforementioned causes of tuyere nozzle failure. Forinstance, to assist the drainage problem the tuyere nozzle can be mounted at a slight downward inclination with respect to the horizontal or the tuyere can be designed to impart a steeper angle to the blast. In an effort to solve the problem of general or local burning of the tuyere nozzle, it has been suggested to thicken the walls of the nose portion, or to include refractory substances in or around the nose portion or to use special water circulation to give preferential circulation to critical areas. Failure due to pressure from the furnace is usually resisted by providing a tuyere wall thickness of approximately one-half inch. Deposits of sediment and creation of gas pockets can be avoided by feeding the cooling fluid in at the bottom of the tuyere nozzle and discharging at the top.

However, in many instances a particular solution for one of the aforementioned causes of tuyere failure results in degradation of the other causes of failure. For instance, the use of heavy nose construction, although demanding a greater extent of abrasion before failure, diminishes the effectiveness of the cooling fluid and, thus, increases the rate of abrasion.

As another example, tuyere nozzles have been cast from a single high conductivity metal such as copper in order to maintain the necessary cool nose but this causes the loss of blast temperature in the heat exchange portion of the tuyere which reduces the efficiency of operation.

SUMMARY OF THE INVENTION AND ITS MOST PREFERRED FEATURES The improved blast furnace tuyere of the present invention overcomes many of the disadvantages and limitations noted above in a novel and simple manner. The tuyere nozzle of the present invention is fabricated from a plurality of elements joined together to form a completed tuyere nozzle. These elements include a copper nose element having high thermal conductivity and a low thermal conductivity pipe or tube, e. g., of stainless steel or ceramic lined metal, extending rearwardly from the nose element to connect with the blast furnace blowpipe at its butt end. The butt element is formed from structurally strong and preferably easily machineable metal, such as steel. The outer element, e. g., of rolled copper alloy, forms a portion of the walls of a heat exchange jacket for cooling the nose element. A baffling element of readily formable metal, such as stainless steel, is preferably provided within the heat exchange jacket to increase the efficiency thereof.

Although this invention is susceptible of embodiment in different forms, one form of the invention is shown in the drawings and which will herein be described in detail, with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the form illustrated.

BRIEF DESCRIPTION OF THE DRAWINGS Further features and advantages of the invention will be apparent from the following description taken in connection with the accompanying drawings wherein;

FIG. 1 is a vertical section of a blast furnace showing the relative locations of the stack. bosh, hearth and tuyeres;

FIG. 2 is a cross-section of a tuyere mounted in the wall of the blast furnace;

FIG. 3 is a longitudinal cross-section of the tuyere nozzle showing the various functional elements thereof;

FIG. 4 is a transverse cross-section of the tuyere taken along the line 4-4 of FIG. 3; and

FIG. 5 is another transverse cross-section of the tuyere nozzle taken along the line 5-5 of FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT My aforementioned TMS-AIME paper includes a discussion of elements and features of this invention and that paper is hereby incorporated herein by reference. The section of the modern blast furnace 10 as shown in FIG. 1 with the parts of the interior previously referred to as the stack, bosh and hearth respectively indicated by reference numerals 12, 14 and 16. A specified volume of air is forced into the blast furnace stove (not shown) which heats the air to the requisite temperature and passes it under pressure through line 18 into the bustle pipe or ring main 20. The ring main 20 surrounds the blast furnace and distributes the hot air to a plurality of circumferentially spaced blow pipes 22 (See FIG. 2) supported by the tuyere stack 23. Each blow pipe 22 is seated into a corresponding tuyere 24 which radially directs the hot air blast through the furnace wall 26 into the hearth 16 to combust the coke therein as previously explained.

Referring now to FIG. 2, a cross-section of a tuyere 24 mounted in the blast furnace wall 26 is shown. The tuyere comprises a body portion or tuyere cooler 30 and a projecting tuyere nozzle 28 which snugly seats into the nose portion of the tuyere cooler 30. The tuyere nozzle is fabricated from different metals which are welded together as will be explained hereinafter, and the tuyere cooler 30 is generally formed from a single metal casting.

The tuyere cooler 30 provides a water cooled port through the furnace wall for the blow pipe and also provides means for mounting the tuyere nozzle 28. The tuyere cooler 30 has an inner cylindrical wall 32 and an outer cylindrical wall 34 which extends through and tits snugly into an opening in furnace wall 26, as shown in FIG. 2. The interior space between walls 32 and 34 of the body portion is cylindrical and annular and receives a continuous flow of cooling water during operation so as to maintain the elements at a relatively low temperature. For this purpose, water circulating pipes 36 and 38 are connected to the body portion. Pipe 38 supplies cooling water to the space formed between the inside and outside walls of the body portion, and the water is discharged from the space through pipe 36.

The tuyere nozzle 28 is a water cooled port through which the hot blast from the blow pipe 22 enters the furnace. The tuyere nozzle includes a nose portion 40 through which the air enters the furnace and a heat exchange portion 42 for cooling the general tuyere area. The nose portion 40 is made of the highest quality conductive copper to withstand the most severe service. The heat exchange portion 42 comprises a tapering generally cylindrical low heat conductivity inner wall or tubular pipe 44 for conveying the hot blast through the tuyere, a tapering generally cylindrical outer wall or tubular body 46 which supplies structural support to the tuyere and a base wall or butt 48 which has a blow pipe seat 52 to connect the blow pipe 22 with the tuyere nozzle.

Tubular pipe 44, tubular body 46, and base wall 48 define a heat exchange chamber 42 in heat receiving proximity with the nose portion through which a cooloccurs in the nose portion where the most severe temperatures exist.

The nose portion 28 and the heat exchange portion 42 are shown in more detail in FIGS. 3-5. The nose portion 40 has an outlet end or outer face 60 with an aperture 62 therethrough for entrance of air into the furnace. A cylindrical inner wall 64 is formed perpendicular with respect to outer face 60 and defines the circumference of aperture 62. A cylindrical outer wall 66 is formed perpendicularly with respect to outer face 60and defines the outside circumference of outlet end wall 60.-

The heat exchange chamber is fabricated by joining the aforementioned elements. The base or butt element 48 has a machined outer surface 67 to fit the nose portion 30 (FIG. 2) and includes a base inlet or outer face 68 and an aperture or bore 70 for entrance of the air blast into the tuyere. The blow pipe seat comprises a machined spherical surface 72 which registers with the nose of the blow pipe (FIG. 2). Outwardly extending cylindrical wall 74 defines the circumference of aperture 70. A second outwardly extending cylindrical wall 76, tapering slightly toward wall 74, corresponds to the circumference of the butt wall 48. At the bottom of outer face 68 an inlet port 75 is provided for connection with water supply pipe 54 and at the top of the outer face 68 an outlet port 77 is provided for connec tion with water discharge pipe,56. The tubular pipe 44 has one end joined to the nose by welding it to inner wall 64 of nose portion 40 in registry with outlet aperture 62 and the other end joined to base 48 by welding it to inner wall 74 of base 48 in registry with inlet aperture 70. Nickel alloys are preferred for welding all dissimilar metals to each other. The tubular body 46 is concentric with, and spaced from, tubular pipe 44. One end of body 46 is joined to nose 40 by welding it to outer wall 66, and the other end is joined to base 48 by welding it to outer wall 76. Finally, the baffle 50 is generally cylindrical and is secured to and supported at one end from the inner surface of base inlet end 68 such as by bolts 50a through an inturned flange 52b, and baffle 50 extends along the length of the heat exchange chamber in spaced relation with the walls thereof. Baffle 50 has a hooked portion 80 at its free end in close proximity to nose portion 40 and the radius of the baffle increases along the length of the tuyere nozzle such that the water passageway defined by the baffle and the tubular body decreases as the water approaches the nose area. This decrease in the volume of the passageway near the nose causes the flow velocity to increase in this area and, thus, provides increased cooling of the nose portion.

The selection of the metals for the various functional elements of the tuyere nozzle is based upon the operational requirements of each element as compared to the comparative properties and characteristics and costs of the metal being considered therefor. In some instances, where the properties of a particular high cost metal are ideally suited for a given element the amount of metal used can be limited to the area having the greatest need to keep costs more reasonable. In other instances several metals may be suitable, and then the least costly metal may be chosen.

The selection of the metal for the nose portion is made with regard to the severe temperature and abrasive conditions that the nose portion must withstand. Abrasion is exclusively confined to the nose portion and to a major degree is dependent upon the cooling function for maintaining the metal at the temperature where its best properties exist. The importance of thermal conductivity must be considered a major factor in determining whether the metal can withstand temperatures well above the melting point. Usually the thermal conductivity of the nose metal will be at least 100 and preferably at least about 200 BTU/sq. ft./hr./F. Of the available high conductivity metals, copper is the preferred for the nose portion.

In choosing a copper alloy for the nose portion, close attention must be paid to the conductivity factor. Coppers conductivity varies widely, with alloy No. 101, OFI-IC copper having a thermal conductivity of 228 BTU/sq. ft./hr./F. and alloy No. 610, ambroloy, an alloy of 92 percent copper and 8 percent aluminum, having a .thermal conductivity of only 40 BTU/sq. ft./hr./F. at 68F./ft. In accordance with the aforementioned conductivity factor, a copper alloy having a thermal conductivity (TC) of approximately 200 BTU/sq. ft./hr./F., such as alloy No. 101 OFHC copper (TC of 228), alloy No. 120 DLP copper (TC of 219), and alloy No. 122 phosphorized copper (TC of 197), is considered suitable for use in forming the tubular body portion.

The quality of the soundness of cast metal is also considered. Technical information indicates that most cast phosphorous deoxidized copper is only about percent sound. In any case one can conclude that the cast copper is not percent sound, and such porosity is a major factor in degrading the total conductivity of the nose formed from east copper. Therefore, it is preferred to use forged or rolled copper, rather than cast copper, in the nose portion to obtain the maximum conductivity of a particular alloy.

Several properties are considered in choosing the metal for the tubing 44 of the pipe section, i. e., a high degree of corrosive resistivity in an operating environment such as encountered in a blast furnace, sufficient strength to withstand the pressures due to the air blast and the cooling water flow, and low thermal conductivity. Copper does not adequately satisfy the last requirement for the pipe section. The standard copper center of the tuyere is responsible for the loss of 10F. of blast temperature. Refractories by themselves do not possess the strength required and are, therefore, combined with higher strength materials, such as metals, when used. On the other hand, stainless steel is a suitable and preferred metal for the tubular pipe section. Stainless steel has a greater corrosive resistivity and a lower thermal conductivity than copper and has sufficient strength to withstand the aforementioned pressures. A considerable savings in fuel can be attained by using a stainless steel or refractory lined metal pipe rather than a copper pipe.

In the preferred form the body wall 46 is composed of strong and conductive metals such as copper or aluminum, while the butt or base 48 is of a strong, readily machineable metal. The preferred metal for the body wall is rolled DLP copper and the preferred metal for the butt is mild steel. Finally, the baffle section can be composed of any rust resistant material having sufficient heat resistance to withstand the hot water (usually less than 212F.) in the heat exchange chamber. Such materials may include plastics such as polyethylene or polystyrene, but metals such as aluminum, stainless steel or galvanized steel are preferable.

Although specific metals or alloys have been chosen, it should be appreciated that the novelty of a fabricated tuyere nozzle made from different metals allows a degree of freedom in tuyere nozzle design that has hitherto before been unknown and the applicant does not intend to be limited to these specific metals or alloys.

I claim:

1. A fabricated tuyere nozzle for a metallurgical furnace, comprising,

a. a preformed annular nose element of high heat conductivity copper alloy having a large central aperture forming a nozzle outlet through which hot gas is directed into a furnace,

b. a low conductivity heat resistant inner tube aligned with the central aperture of the nose element and having one end joined to the nose element,

c. a heat conductive outer tube in spaced relation around the inner tube and having one end joined to the nose element and forming a heat exchange chamber between the tubes,

. a butt end plate spanning the inner and outer tubes and joined to the butt ends of the tubes remote from the nose element and closing the heat exchange chamber,

. an inlet and an outlet for heat exchange fluid in the end plate, and

f. means within said heat exchange chamber for directing heat exchange fluid from the inlet to the nose element and then to the outlet.

2. A fabricated tuyere nozzle as defined in claim 1,

wherein said nose element is composed of a forged or wherein said butt end plate is composed of steel.

. A fabricated tuyere nozzle as defined in claim 1,

wherein said fluid directing means is a tubular element secured to and supported at one end by said butt plate,

extends forwardly from the butt plate to a position adjacent the inner surface of the nose element and includes an enlarged baffle portion at its forward end for restricting and increasing flow rate at the nose element.

8. A fabricated tuyere nozzle as defined in claim 1,

wherein the inner and outer tubes are separate from the nose element and butt end plate, and welded to both.

9. A fabricated tuyere nozzle for a metallurgical furnace, comprising,

a. a preformed annular nose element of heat conductive copper alloy having a U-shaped cross section including an end wall, an outer wall and an inner wall defining a large central aperture forming a nozzle outlet through which hot gas is directed into a furnace,

. a stainless steel inner tube of lower thermal conductivity and greater strength than the nose element aligned with the inner wall of the nose element and welded thereto,

. a heat conductive outer tube of copper alloy aligned with the outer wall of the nose element and secured thereto, forming a heat exchange chamber between the tubes,

. a butt end plate of steel having forwardly extending walls respectively welded to the inner and outer tubes at the end remote from the nose element, closing the heat exchange chamber,

. a generally cylindrical baffle in the heat exchange chamber secured to the end plate and extending forwardly into the nose element concentric between the inner and outer walls thereof for directing heat exchange fluid to the nose element, and

f. an inlet in the end plate for supplying heat exchange fluid to the space between the inner tube and the baffle, and an outlet in the end plate for discharging heat exchange fluid from the space between the baffle and the outer tube.

* B i 1 i 

1. A fabricated tuyere nozzle for a metallurgical furnace, comprising, a. a preformed annular nose element of high heat conductivity copper alloy having a large central aperture forming a nozzle outlet through which hot gas is directed into a furnace, b. a low conductivity heat resistant inner tube aligned with the central aperture of the nose element and having one end joined to the nose element, c. a heat conductive outer tube in spaced relation around the inner tube and having one end joined to the nose element and forming a heat exchange chamber between the tubes, d. a butt end plate spanning the inner and outer tubes and joined to the butt ends of the tubes remote from the nose element and closing the heat exchange chamber, e. an inlet and an outlet for heat exchange fluid in the end plate, and f. means within said heat exchange chamber for directing heat exchange fluid from the inlet to the nose element and then to the outlet.
 2. A fabricated tuyere nozzle as defined in claim 1, wherein said nose element is composed of a forged or rolled copper alloy having a thermal conductivity of at least about 220 BTU/sq. ft./hr./*F and forms a wall portion of the heat exchange chamber for direct contact of the nose element inner surface with heat exchangE medium within said chamber.
 3. A fabricated tuyere nozzle as defined in claim 1, wherein said inner tube is composed of stainless steel.
 4. A fabricated tuyere nozzle as defined in claim 1, wherein said outer tube is composed of a rolled copper alloy.
 5. A fabricated tuyere nozzle as defined in claim 1, wherein said butt end plate includes an outer sealing surface engageable with a surrounding cooling element for sealing the furnace and an inner sealing surface engageable with a blowpipe for sealing the blowpipe.
 6. A fabricated tuyere nozzle as defined in claim 1, wherein said butt end plate is composed of steel.
 7. A fabricated tuyere nozzle as defined in claim 1, wherein said fluid directing means is a tubular element secured to and supported at one end by said butt plate, extends forwardly from the butt plate to a position adjacent the inner surface of the nose element and includes an enlarged baffle portion at its forward end for restricting and increasing flow rate at the nose element.
 8. A fabricated tuyere nozzle as defined in claim 1, wherein the inner and outer tubes are separate from the nose element and butt end plate, and welded to both.
 9. A fabricated tuyere nozzle for a metallurgical furnace, comprising, a. a preformed annular nose element of heat conductive copper alloy having a U-shaped cross section including an end wall, an outer wall and an inner wall defining a large central aperture forming a nozzle outlet through which hot gas is directed into a furnace, b. a stainless steel inner tube of lower thermal conductivity and greater strength than the nose element aligned with the inner wall of the nose element and welded thereto, c. a heat conductive outer tube of copper alloy aligned with the outer wall of the nose element and secured thereto, forming a heat exchange chamber between the tubes, d. a butt end plate of steel having forwardly extending walls respectively welded to the inner and outer tubes at the end remote from the nose element, closing the heat exchange chamber, e. a generally cylindrical baffle in the heat exchange chamber secured to the end plate and extending forwardly into the nose element concentric between the inner and outer walls thereof for directing heat exchange fluid to the nose element, and f. an inlet in the end plate for supplying heat exchange fluid to the space between the inner tube and the baffle, and an outlet in the end plate for discharging heat exchange fluid from the space between the baffle and the outer tube. 